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Modify Numpy seed restriction #691

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Sep 12, 2025
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Modify Numpy seed restriction #691

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8 changes: 7 additions & 1 deletion CHANGELOG.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -5,11 +5,17 @@ Changelog
Unreleased
----------

* Removed the random state caching, which would grow without bound, leaking memory in long test runs.
* Remove the random state caching, which would grow without bound, leaking memory in long test runs.
The caching was added to slightly speed up re-using the same (final) seed, but since the final seed is now different for each test, it has no effect.

`PR #690 <https://github.com/pytest-dev/pytest-randomly/issues/687>`__.

* Modify Numpy seed restriction, replacing hashing with a modulo operation.
The extra work to hash is unnecessary now that we generate a final seed per test with CRC32.
This change saves ~500ns per test when Numpy is installed.

`PR #691 <https://github.com/pytest-dev/pytest-randomly/issues/691>`__.

4.0.0 (2025-09-10)
------------------

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17 changes: 3 additions & 14 deletions src/pytest_randomly/__init__.py
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@@ -1,7 +1,6 @@
from __future__ import annotations

import argparse
import hashlib
import random
import sys
from functools import lru_cache
Expand Down Expand Up @@ -160,8 +159,7 @@ def _reseed(config: Config, offset: int = 0) -> int:
baker_random.setstate(random_state)

if have_numpy: # pragma: no branch
numpy_seed = _truncate_seed_for_numpy(seed)
np_random.seed(numpy_seed)
np_random.seed(seed % 2**32)

if entrypoint_reseeds is None:
eps = entry_points(group="pytest_randomly.random_seeder")
Expand All @@ -172,15 +170,6 @@ def _reseed(config: Config, offset: int = 0) -> int:
return seed


def _truncate_seed_for_numpy(seed: int) -> int:
seed = abs(seed)
if seed <= 2**32 - 1:
return seed

seed_bytes = seed.to_bytes(seed.bit_length(), "big")
return int.from_bytes(hashlib.sha512(seed_bytes).digest()[: 32 // 8], "big")


def pytest_report_header(config: Config) -> str:
seed = config.getoption("randomly_seed")
_reseed(config)
Expand All @@ -189,7 +178,7 @@ def pytest_report_header(config: Config) -> str:

def pytest_runtest_setup(item: Item) -> None:
if item.config.getoption("randomly_reset_seed"):
_reseed(item.config, _crc32(item.nodeid) - 1)
_reseed(item.config, (_crc32(item.nodeid) - 1) % 2**32)


def pytest_runtest_call(item: Item) -> None:
Expand All @@ -199,7 +188,7 @@ def pytest_runtest_call(item: Item) -> None:

def pytest_runtest_teardown(item: Item) -> None:
if item.config.getoption("randomly_reset_seed"):
_reseed(item.config, _crc32(item.nodeid) + 1)
_reseed(item.config, (_crc32(item.nodeid) + 1) % 2**32)


@hookimpl(tryfirst=True)
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